[Asterisk-Users] UDP Fragmentation Problem

[Bastian Schern]

Rich Adamson schrieb:
>>>>>I've got no success to get a friend in Bogota (Colombia) connected to my
>>>>>Asterisk. He has got a ISDN Internet connection and the UDP packets will
>>>>>be fragmented. It seems that the MTU of this connection is round about
>>>>>400 to 500 Bytes. Therefore most UDP-SIP packages are fragmented.
>>>>>Is Asterisk not able to handle fragmented UDP packages?
>>>>>Is it possible to use SIP over TCP with X-Lite?
>>>>>Or has somebody another hint for me?
>>>>
>>>>
>>>>
>>>>As far as I am aware there is no such thing as a fragmented UDP 
>>>>packet; each packet is sent out on its own, there is no coherency 
>>>>between UDP packets like there is with TCP packets.
>>>>
>>>>I could be very wrong here, it's been a late night with the kids.  :-)
>>>>
>>>
>>>Packet fragmentation is at the IP layer, so UDP will have fragmented 
>>>packets too. But... the OS should handle that and Asterisk shouldn't 
>>>find out - it's a all or none policy, so it should receive the whole 
>>>packet at once or nothing.
>>
>>How I can setup Linux to handle UDP fragments?
> 
> 
> Not sure why the concern with fragmentation, it should not be an issue 
> with any modern linux distribution and there is nothing to setup.
> 
> The only issue that I've heard about in recent months/years relative
> to fragmentation is the SonicWall firewall just can't seem to get it
> right. In their case, any udp packet greater then about 1500 bytes does
> not get reassembled propery, and its still an issue in the latest firmware.
> 
> If you really think you've got a fragmentation problem, I'd like to see
> a packet trace (eg, ethereal) of those packets.
> 

Here it is ;-)

Regards
	Bastian
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